Evaporator bodies for PVD coating systems and methods for the production thereof are known, for example, from DE 10 2005 030 862 B4, to which reference is made.
The evaporator bodies can be used in vacuum metallization systems, in which a metal is deposited onto a substrate by means of PVD (physical vapor deposition) technology. The metallization systems are used particularly to coat flexible substrates with metals, particularly with aluminum. Films, particularly plastic films, may be used as substrates. The coating material is continuously fed to the heated evaporator body and evaporates on an evaporator surface of the evaporator body in a vacuum.
The evaporator body is preferably a ceramic body, which contains titanium boride and boron nitride as the main components and which can be adjusted to a specific electrical resistance of, for example, 600 to 6000 μΩ cm through a suitable mixture of these materials. The evaporator body contains the components titanium boride and boron nitride typically in about equal portions of about 50% by weight each, plus/minus about 5% by weight. The heating of the evaporator body typically takes place by applying a heating current.
For continuous coating with the highest possible processing speed, the adjusting of the evaporation parameters is of decisive significance. It is especially important that the evaporator surface of the evaporator body be as homogenous as possible and be completely wetted with the material to be evaporated, particularly aluminum.
Various measures are already known from the prior art for improving the wetting of the evaporator surface.
DE 10 2005 030 862 B4 discloses the use of a first-wetting auxiliary material, which is applied to the evaporator surface before the initial use of the evaporator body in a coating system. The first-wetting auxiliary material may be applied or even painted on as a paste or as a suspension. It contains powdery aluminum as well as additional powdery wetting agents. When heated, the aluminum combines with the boron nitride of the evaporator body to form aluminum nitride, which exhibits improved wetting behavior for aluminum in comparison with boron nitride. By applying the first-wetting auxiliary material, a wetting coat is thus formed by reacting the aluminum with the boron nitride. The further powdery wetting agents are, for example, titanium, titanium diboride, zirconium, zirconium diboride, molybdenum, or even metal alloys. These further powdery wetting agents facilitate a maximum widespread distribution of the aluminum that melts when the evaporator body is heated. In addition to creating a wetting layer made of aluminum nitride, the particular advantage is thus also achieved that the evaporator surface is homogenously wetted with the then liquid aluminum right at the start of the evaporation process due to the integration of the aluminum into the first-wetting auxiliary material.
US 2009/0217876 A1 discloses a coating system for extending the service life of a ceramic evaporation boat. The coating system comprises a ceramic layer on the surface of the evaporation boat. Optionally, a heat-resistant metallic layer is applied between the surface of the evaporation boat and the ceramic layer. The ceramic material of the ceramic layer is selected from metal borides, metal nitrides, metal carbides, metal oxides, and combinations thereof, wherein the metal component of the ceramic material is selected from zirconium, aluminum, titanium, silicon, tantalum, vanadium, and combinations thereof. The coating thickness of the ceramic layer is preferably between 1.5 and 5 μm.
WO 2006/117119 A1 describes an evaporation boat comprising an electrically conductive ceramic carrier material for the evaporation of substrates with metals, wherein on the surface of the evaporation boat from which the evaporation of the metals takes place, one of the following coatings is provided: a) a coating of at least one boride of a transitional metal from Group 4 to 6 of the Periodic Table, b) a coating from a mixture of the metal to be evaporated and at least one transitional metal from Group 4 to 6 of the Periodic Table and/or the borides thereof, c) a first coating from at least one transitional metal from Group 4 to 6 of the Periodic Table and/or the borides thereof and a coating applied thereto comprising a metal to be evaporated. The evaporation boats should exhibit good initial wetting for the metals to be evaporated such that the evaporation can be implemented with minimal spatter and uniformly.
U.S. Pat. No. 6,645,572 B2 and DE 10 2004 009 335 A1 relate to metal and evaporation boats comprising a ceramic material for saving electric power during evaporation comprising an electrically conductive component and an electrically non-conductive component, wherein the electrically conductive component of the ceramic material is enriched on the contact surface of the evaporation boat.
U.S. Pat. No. 4,810,531 discloses a method for the chemical vapor deposition of tin, in which an evaporator body comprising boron nitride is provided with an evaporation layer, to which a dispersion containing titanium hydride is applied. The titanium dihydride in this case is dispersed in a chlorinated organic solvent, preferably carbon tetrachloride. As the evaporator body is heated, the solvent evaporates and a titanium hydride layer remains as a wetting layer, which is intended to improve the wetting behavior for tin as the material to be evaporated. The thickness of the titanium hydride layer is about 0.1 mm.
U.S. Pat. No. 2,756,166 discloses a further PVD coating system, in which coated carbon rods are used as the evaporation bodies. The carbon rods are equipped with a suspension containing titanium hydride, wherein the titanium hydride decomposes into metallic titanium and hydrogen gas when heated. The metallic titanium then reacts in turn with carbon from the carbon rods used to form titanium carbide in order to thus form a wetting layer.
DE 10 2013 218 322 A1 describes an evaporator body for a PVD coating system, which comprises a basic body with an evaporator surface, to which an aluminum titanium wetting layer is applied. Upon delivery, a layer containing two reactants, particularly aluminum and titanium dihydride, is applied to the basic body. When the basic body is heated to about 1500° C., the two reactants form the wetting layer. The layer with the two reactants is applied from a suspension to the evaporator body, which has a thickness of about 0.1 to 0.2 mm.